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Boost Vs. Compression
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AznDrgn  
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PostPosted: Thu Mar 14, 2002 4:23 am    Post subject: Reply with quote

Is there some kind of rule of thumb or a chart that you can look at to figure out how hight you can crank the boost up on a car? I'm going to turbo charge my '78 924NA and I don't intend to change anything just add the turbo and an intercooler.

Thanks
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Rick MacLaren  
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PostPosted: Thu Mar 14, 2002 7:14 am    Post subject: Reply with quote

"...I don't intend to change anything just add the turbo and an intercooler"

One word comes to mind:
















BOOM

[ This Message was edited by: Rick MacLaren on 2002-03-14 08:15 ]
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Alex Roy  
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PostPosted: Thu Mar 14, 2002 7:28 am    Post subject: Reply with quote

I don't think there will be any "Boom" involved.

There was the BAE turbo kit and also the Windblown kit, and they did precisely that, add a turbo (they didn't even add an intercooler).

I am personally bolting on the BAE kit on my car and have a front mount Starion/Conquest intercooler, Give me a couple weeks (..er, months) and I should be "finished" with my install (and I am using the euro pistons and a fully rebuilt engine).

There are many Honda/Acura kits for bolt on turbos, and their compression ratio is generally high, and I haven't heard of too many problems with those set-ups.
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JvGinPDX  
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PostPosted: Thu Mar 14, 2002 8:55 am    Post subject: Reply with quote

Alex, I want to hear how things turn out for you. I have an early 77, with the 8 to one compression, the engine is in good shape. Has anyone elso on the board turboed their car? How are things working out?
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2743
Location: Sydney, Australia

PostPosted: Thu Mar 14, 2002 10:55 am    Post subject: Reply with quote

one word comes to mind..

EMS (OK that's really 3 words). The reason you can turbo modern hi-compression engines without problems is that the knock sensors will alert the ems when detonation starts occuring and the ems will retard the spark.

Without going for a programmable ems, which probably wouldn't help because of the lack of knock sensor input, you need to run fairly low boost and possibly retard your ignition. What "fairly low boost" means can only be determined when you tune it, preferably on a dyno.

If you're running US 8.5 pistons and an intercooler you should be able to run boost similar to a 931, say 8psi. When you think about it, 8.5:1 compression in a modern turbo engine is about standard. If detonation is a problem you can always go for water/alchohol injection but you would probably be better off reducing the boost
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AznDrgn  
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PostPosted: Fri Mar 15, 2002 12:25 am    Post subject: Reply with quote

So in order for me to run boost any higher I'll need to get the timing retarded and or get a more efficient intercooler? For timing retardation I was thinking about getting an MSD 6BTM which allows me to retard timing according to how much boost is being produced. The timing settings might take a little trial and error but I think it will work. Intercooler wise I was thinking of either a water cooled system or using the ac system to chill the air. Let me know what you think, am I just wasting money or is something like this worth looking into?


Thanks
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Alex Roy  
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PostPosted: Fri Mar 15, 2002 2:16 am    Post subject: Reply with quote

I would say "go for it". I would recomend going for the 6btm or something similar so you have some extra control, worst case, you would only be able to run 6-8 psi, and that would still be more fun than the stock N/A.
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Rick MacLaren  
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PostPosted: Fri Mar 15, 2002 3:05 am    Post subject: Reply with quote

Oh?

Hmmm.

I have a friend, who, about 7 years ago, sold a BAE kit to one of our colleagues here on the board, intercooler and all...and the result (because his budget was not unlimited)...


















BOOM

(and it was a really nice NA 924)

Good luck.



[ This Message was edited by: Rick MacLaren on 2002-03-15 04:21 ]
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jamez  
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PostPosted: Fri Mar 15, 2002 3:20 am    Post subject: Reply with quote

get the SDS fuel injection/engine management system, it comes with a knock sensor, it will also retard timing, man it does everything..
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Alex Roy  
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PostPosted: Fri Mar 15, 2002 3:20 am    Post subject: Reply with quote

If you want, wait for me to get my engine up-and-running.

I'll be the guineypig.

Rick-what condition was the colleagues engine in before the turbo was installed, and did he have an intercooler, retarded spark, a boost gauge, an Air/Fuel gauge so he knew what his engine was doing?
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Rick MacLaren  
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PostPosted: Fri Mar 15, 2002 4:16 am    Post subject: Reply with quote

Yeah well you see, Alex, the questions you ask are all about the person having MORE than just a turbo and intercooler, aren't they?

The writer of the note said, and I quote:

"...I don't intend to change anything just add the turbo and an intercooler"

To answer your question, the engine the guy used was fine. Did he play with timing? Yes. Did he have a boost gauge? Yes. Air/Fuel gauge? No.

In a book I used when rebuilding my 931 engine, called "Super Power" (a kitschy title but appropriate) the writer notes a few needed things to do to a normally aspirated engine before just installing a turbo and intercooler, notably:

Lower compression - common tactic = dished pistons

Increase fuel flow

Balanced engine

Rods hardened or treated

New valve springs (Turbos make the springs work way harder to battle against the boost)

Valves three point grind

Head rebuilt

Modified intake to withstand boost

Redo the engine cooling and oil cooling to accommodate higher temperatures

Etc.

Look, it doesn't matter to me what the guy does Alex, but a simple solution like this...

"...I don't intend to change anything just add the turbo and an intercooler"

...will just end up costing the man money. I should know, I've done it (blown up) with a real turbo and learned my lesson well. I'm just hoping that by using the term "BOOM" I'm able to drive home to the man that a little more care is needed than just a bolt-on solution.

[ This Message was edited by: Rick MacLaren on 2002-03-15 05:17 ]
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Alex Roy  
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PostPosted: Fri Mar 15, 2002 4:49 am    Post subject: Reply with quote

Good point. I wasn't going off of the original question, I was going off of the last post which DID talk about a timing computer.
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Rick MacLaren  
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PostPosted: Fri Mar 15, 2002 5:48 am    Post subject: Reply with quote

Ok yes. My mistake. I thought you were lending support to the idea of just tossing on the IC and turbo.

I'm struggling a bit with the computer question now too. You have a Haltech. I'd like to get one of these units but they're a bit rich for my blood right now.

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AznDrgn  
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PostPosted: Fri Mar 15, 2002 8:39 am    Post subject: Reply with quote

It's still going to be quite a while before I start messing with the turbo. Just trying to get an idea of what I need and how much it is going to cost me. I also need to figure out how to get a manifold that I can mount a turbo to, I was trying to get that BAE that was on e-bay but WOW that went up high in the last 20 min. Alex you'll probably get this done way before I do so let me know how it goes.
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jamez  
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PostPosted: Fri Mar 15, 2002 8:56 am    Post subject: Reply with quote

I was trying to get that BAE too, but I didn't want to pay over $250 for it. I can't believe it went for so high..
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